support range 0001-01-01 to 9999-12-31 for dates

[tswast]

Currently, the date data type only supports a range of a few hundred years (nanoseconds since 1970-01-01 in a 64-bit integer). It'd be nice if there was an (optional) way to support a wider range.

One possible way to do this would be to store in different units (I think microsecond would be sufficient), but that could cause operations such as combining a date + time column into a datetime / timestamp column to be more complex.

Alternatively, we could provide a suite of thin wrappers around the pyarrow date types. This might be better accomplished by a different package such as Fletcher, though.

[tswast]

Marking as duplicate of #63